Waveguide pressurizing plug



Sept. 19, 1961 T. KINAGA 3,001,158

WAVEGUIDE PRESSURIZING PLUG Filed Feb. 1, 1956 7 3,001,158 WAVEGUEDE PRESSURIZING PLUG Thox'nas Kinaga, Los Angeles, Calif., assignor to Hughes- Aircrait Company, Culver City, Caliii, a corporation of Delaware Filed Feb. 1, 356, 821'. No. 562,684 Claims. ((11. 33398) This invention relates to waveguide closure members for wave energy transmission systems and more particularly to a waveguide closure member which is transparent to electromagnetic wave energy when the antenna of the system is utilized to emit energy in one medium and which is an impedance transformation element to couple the system to a liquid medium to enable the liquid medium to act as a dummy load when the antenna of the system is in a liquid medium.

Electromagnetic wave energy transmission systems comprising a transmitter and a wave energy antenna coupled to the transmitter are frequently used on submersible vehicles such as submarines. Although the wave energy transmitting system is not operative underwater, it is frequently undesirable to deenergize the transmitter when the vehicle is submersed, for the reason that the system may be again called into service within a short duration, and the operation of the same is not sufficiently stable until after an adequate warmup period. The use of the equipment in its energized state under water is likely to result in serious damage as the result of severe reflection of wave energy from the antenna back into the transmitting system, due to impedance mismatch at the antenna due to the water medium facing the same. It is necessary, therefore, in order to permit a wave energy transmitter to be maintained in an active state even though submerged in a liquid such as water, that provision be made to prevent serious reflection of wave energy at the antenna.

It is accordingly a prime purpose of the present invention to provide a device for use in connection with waveguide antennas which will be transparent to electromagnetic wave energy when the antenna is in the medium for which it was designed, for example air, and which will provide an unreflecting transformation section to couple the system with a liquid medium such as water. Under this condition the water is utilized as an energy absorber. This purpose is accomplished by the provision of a dielectric closure member having a particular configuration for transformation purposes and which also provides a hermetic closure element for the waveguide system.

The above and other objects and advantages will become apparent from the following description and accompanying drawings.

In the drawings FIG. 1 is a three dimensional phantom view of the device of this invention positioned in a waveguide.

FIG. 2 is a section taken through the closure member of FIG. 1 along the section line 2-2.

FIG. 3 is a section taken through the closure member of FIG. 1 along the section line 3--3.

Referring to the figures of the drawings and particularly to FIG. 1, the waveguide closure member of this invention comprises an elongated, thin wall, dielectric open-ended box member 12 having a cross-sectional size and shape to correspond to and closely fit the interior of the waveguide 14. A dielectric septum 16 is hermetically afiixed within the dielectric box member 12 normal to the planes of the sides thereof and approximately midway between the open ends. A plurality of elongated planar dielectric strips 18 are afiixed, normal to the walls of the septum 16 on opposing sides thereof, and in planes normal to the design direction of the electric vector of wave energy to be propagated by the waveguide. FIGS. 2

3,l,153 Patented Sept. 19, 1961 ice and 3 show with some more particularity the arrangement existing between box member 12, the septum 16 and the strips 18 of the waveguide closure member 10 of FIG. 1.

The closure member in FIG. 1 was designed to withstand a pressure of 500 pounds per square inch and transmit wave energy for search, having a working wavelength of about 32.2 centimeters, and wave energy for identification, having a working wavelength of about 64.4 centimeters. The length of the closure member, which has a composite dielectric constant somewhere between 1 and 3.8, is about 15.5 centimeters so that it acts as a onewavelength window to the search waves and as a halfwavelength window to the identification waves. The cross-sectional area of the box member is about 6% x' 3% inches to permit insertion into the waveguide. The thickness of the septum is about V2 inch which is sufiicient to withstand the above-named water pressure.

The waveguide closure member may be made from slabs of a dielectric material containing 96 of silica and 4% impurities. Such a dielectric is manufactured by the Coming Glass Works, Corning, New York, as Vycor, under the Code Series No. 7900. The dielectric constant of this dielectric material is about 3.8. The slabs may be cemented together wth a glue comprising an epoxy resin combined with asbestos filler and aluminum oxide filler to which is added a curing agent such as amine. Such a glue is manufactured by the Shell Chemical Corporation, 380 Madison Avenue, New York 17, New York, under the name of Epon Adhesive VIII. This glue may also be used to cement the closure member into the waveguide section to obtain a hermetic seal. To prevent stresses due to changes of temperature, the waveguide section may be made of Invar, a nickel steel containing about 36% nickel, whose coeflicient of expansion is very small.

It is to be understood that the above depicted and described closure member is but representative of the in vention, and the dimensions and material specifications are not to be interpreted in any way in a limiting sense since many possible modifications and alterations of the closure assembly may be made within the scope of the appended claims.

What is claimed is:

1. A closure member for a waveguide comprising: an elongated dielectric box member having lateral walls and open ends and having the lateral walls supported adjacent and hermetically sealed to the inner walls of said wave guide; a thin dielectric septum located within said box member perpendicular to the lateral walls of the same, said septum being hermetically aifixed at its edges to the lateral walls of said box member; and a plurality of parallel, planar dielectric strips separated from one another and affixed perpendicularly to the opposing faces of said septum and extending across said box member, said closure member being of predetermined length.

2. A closure member for a Waveguide adapted to propagate wave energy comprising: an elongated dielectric box member having lateral walls and open ends and having the lateral walls supported adjacent and hermetically sealed to the inner walls of said waveguide; a dielectric septum located midway within said box member and perpendicular to the lateral walls of the same, said septum being hermetically atfixed at its edges to the lateral walls of said box member; and a plurality of parallel,

equally spaced planar dielectric strips spatially separated to provide an opening and aflixed perpendicularly to the opposing faces of said septum and extending across said box member, said closure member having a length equal to m where A is the working wavelength of the wave energy within said closure member when said closure member is exposed to air, and n is any integer.

3. A closure member for a waveguide adapted to propagate wave energy comprising: an elongated dielectric box member having lateral walls and open ends and having the lateral walls supported adjacent and hermetically sealed to the inner walls of said waveguide; a thin dielectrio septum located midway Within said. box member. and perpendicular to the lateral walls of. the same, said septum being, hermetically afiixed at its. edges. to the: lateral walls of said box member; and a plurality of parallel, equally spaced planar dielectric. strips separated from one an.- other by a distance substantially equal to the thickness or said. strip and affixed perpendicularly tothe opposing faces of said septum and extending across said box. member, the length of said closure member being selected to be an integralmultiple of half Wavelengths of the working wave energy passing therethrough upon transmission.

1 '4. A closure member for a waveguide. adapted to propagate Wave energy comprising: an-v elongateddielectric box member having lateral walls and open ends and having the lateral walls supportedadjacent and hermetically sealed to the inner walls of said waveguide; a thin dielectric septum locatedv midway within said box member and perpendicular to the laterfl; walls. of: the same, said septum being hermetically aflixed at itsedges to. the: lateral walls of said box member; and a. plurality of parallel, equally spaced planar dielectric strips perpendicularly med to the opposing faces of saidseptum andv extending across said box member, the length of said closure member being selected to be an. integral multiple of half wavelengths of the. working wavelength with said closure member when said closure member is transmitting into an air medium.

5. A closure member for a waveguide comprising: a dielectric box member of predetermined length defining an axially extending opening and hermetically sealed to the inner walls of said waveguide; a thin dielectric septum centrally located within said box member and disposed perpendicular to the. direction of said extending opening, said septum supported at its extremities by said box member and hermetically sealing. said extended opening; and a plurality of laterally disposed, equally spaced planar dielectric strips extending across said opening on either side of said septum, each strip supported at opposite ends by said box member and at one. end. by said septum parallel tothe remaining strips and perpendicularly to said septum, the effective length of said closure member being an integral multiple of half. wavelengths of the working wavelength withinsaid closure member when the medium or either side of said septum is air.

References Cited in the tile of this patent UNITED STIIAFFES PATENTS 1,990,649 Ilberg Feb. 12, 1935 2,407,911 Tonks et a1 Sept. 17, 1946 2,511,610 Wheeler June 13, 1950 2,577,158 Rosencrans' Dec. 4, 1951 2,577,463 Hansell Dec. 4, 1951 2,611,869 Willoughby Sept. 23, 1952 

